Many fill valves for toilet tanks have a pilot operated main valve which has a small flexible valve diaphragm that has a central small passage therethrough for allowing water pressure to seep behind the valve, thereby pressing the valve against a valve seat to shut off the main fill valve. A chamber behind the main valve diaphragm has a small relief aperture which when open alleviates pressure in the chamber. When it is desired for the main valve to be closed, that relief aperture is closed off by a pad operated by a floating ball cock or a diaphragm responsive to air pressure or water pressure.
The relief hole in the chamber and passage through the main valve diaphragm are small. It is therefore important that the water supply through the fill valve is clean, absent any large particles that may block the aperture or passage or otherwise interfere with the function of the fill valve parts. It is common to have a screen mounted at the upstream end of the fill valve riser conduit. These screens, when clean, work fine. However, once the screens have been blocked by particles and other debris, one must unhook the fill valve from the water supply conduit. The water supply conduit is often located at the bottom of the tank behind the bowl in an often tight and uncomfortable position. Because of the unpleasantness of unlinking the supply conduit, the screens are often left unclean which unduly blocks the water supply to the fill valve and consequently slows the flow to refill the tank. Consequently, a toilet refill cycle is unduly extended.
U.S. Pat. Nos. 4,574,826 and 4,646,779 issued to Dwight N. Johnson on Mar. 11, 1986 and Mar. 3, 1987, respectively, disclose an adjustable fill valve which has a telescopic riser conduit which is separable from the lower riser conduit section that is mounted at the bottom of the tank. The upper section has a basket strainer attached to the bottom end of the telescopic riser conduit. The basket strainer can be cleaned when the fill valve is disassembled and the telescopic upper riser conduit is removed from the lower conduit section. A flow restrictor is also mounted at the bottom end of the telescopic conduit section.
What is needed is a high capacity strainer which can strain a large amount of debris without the need for cleaning and in which the strainer can be cleaned or flushed without disassembly of the supply conduit or removal of the strainer from the riser conduit.